Boletín de aludes

East Slopes Central

Northwest Avalanche Center
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Peligro de aludes

Mon
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó 5 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

The likelihood of a very large avalanche ticks downward each passing day without a new event.  However, the consequences of a deep slab avalanche remain the same and should still dictate how you travel.  Avoid traveling on large open slopes and limit your overhead exposure throughout the weekend.

Problemas de aludes

  • Deep Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    3

    Every day without a new deep slab avalanche is a step in the right direction.  We are nearly a week out from the last known deep slab avalanche but our uncertainty around this problem remains high.  Much cooler temperatures arrived Saturday, another welcome sign following several days of above freezing temperatures earlier in the week.  A trend in the right direction is not enough to overcome the deadly consequences of a deep slab avalanche.  Be intentional about where and how you travel.  If you flip through some of the photos in the media reel below, you'll see some of these monster avalanches have coursed thousands of feet, broken mature trees, and pushed through areas you might not normally think twice about stopping. 

    The way to stay safe is simple: Avoid traveling in or lingering under large avalanche paths. Use extra caution on any steep slope, even around sparse trees. Before you commit to traveling in avalanche terrain, ask yourself, "What's the largest avalanche that this slope can produce, am I willing to take that risk, and is there a safer option?"

    (3/1/2021) A very large avalanche (D3) was triggered by WSDOT highway forecasters on March 1st in a portion of the West Camp path on Rock Mtn. Adjacent sections of this avalanche path ran naturally on Feb 26th. Photo: WSDOT

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1

    There's just enough new snow along with moderate to strong ridgeline winds late Saturday night through Sunday that fresh wind slabs should develop on lee slopes above treeline.  Shooting cracks or hollow-sounding snow are signs you could trigger an avalanche on similar slopes. Steer around obvious wind features like freshly drifted snow and wind pillows.  Avoid steep slopes below cliff bands where spin drifts may form localized wind slabs that could release naturally or with your help.  If you find that similar conditions extend further down in elevation,  seek out lower angle and wind-sheltered terrain.  Triggering a wind slab avalanche could be the right-sized poke to wake up deeper slabs lingering in large avalanche terrain. 

    Example of a small wind slab releasing below cliffs in the Mission Ridge area this winter.

Avalanche Discussion

The start of March marked a change from our cold and snowy February with mild temperatures, periods of sunshine and freezing levels hovering between 5000-7000'.  A weather system brought an inch or two of snow to the East Central zone along with cooler temperatures by Saturday morning.  Cooler temperatures will help decrease the chance of cornice fall over the weekend.  A fresh round of wind and light snow will arrive on Sunday. This time, there should be enough new snow near the Cascade crest to drive a new wind slab problem. 

The last major storm cycle occurred February 25-26th with ~2" of water equivalent at the Cascade Crest and extreme winds. This came on the heels of an even bigger storm.  From Feb 20-23rd, a massive storm brought up to 6" of water equivalent to the mountains near the crest but much less to the Wenatchee Range further east. Numerous deep and very wide avalanches (Many D3-3.5's, some size D4's)  ran on, or around the 22nd in the mountains near the crest, and some deeper slabs were reported from the Wenatchee Range. Similar-sized avalanches continued earlier this week.

An observer on Wednesday reported widespread very large avalanches in the Chiwaukum range and the Icicle drainage from the most recent cycle. While conditions may be less dangerous in parts of the Wenatchee Mountains, due to less recent snow, the same weak layers can be found and recent avalanches have been triggered on them. In the northern end of the zone, near Holden, the mid-January weak layer is present, though it has produced inconsistent test results. An observer there reported that most avalanches from late February appeared to run on storm interfaces in the upper snowpack.

Recent notable avalanches:

3/1: WSDOT avalanche teams observed a recent (within the past 24hrs) natural D3.5 deep slab from high, north-facing terrain in the Chiwaukum Range. They also triggered an 8ft deep D3 in southeast facing terrain at around 6,000ft off Rock Mountain east of Stevens Pass (the remaining hangfire in West Camp path). Chair Peak at Snoqualmie Pass ran as a D3.5 at some point between Sunday night and Monday morning (3/1) with a crown 10-15'+ deep. An observer reported numerous very large avalanches near Fortune Peak, just west of this zone.

2/28: A fairly fresh-looking deep persistent slab avalanche from upper elevation terrain was spotted in the Chiwawa drainage. 

2/26-27: A natural D4 avalanche released from Rock Mtn and came just short of Highway 2. A couple of D2.5-3's terrain in Icicle Creek (see photo below).

Check out the Conditions blog for a more comprehensive and regional summary of very large avalanches that have released throughout the central and southern Cascades over the past two weeks.

Regiones cubiertas